1. Field of the Invention
The present invention relates to a low capacitance chip varistor and a fabrication method thereof, and in particular to an improved low capacitance chip varistor and a fabrication method thereof which are capable of protecting the electronic elements of an electronic appliance from an external or internal surge and being well applicable to an electronic element which requires a low capacitance.
2. Description of the Conventional Art
Recently, as the electronic appliance is made lighter and compact in size and has multiple functions, a high density mounting technique is rapidly developed using a surface mounting device (SMD). Since a signal transmission speed of a surface-mounted device circuit exceeds MHZ unit, the capacitance should be lowered below 10 pF for enabling a high speed signal transmission and a faster operation of the circuit. More preferably, the signal transmission speed is required to be lowered below 5 pF.
In order to meet the above-described requirements, a disc type varistor is intensively studied as one of chip types. The chip varistors formed by stacking method have many problems to make low capacitance one since the material composing the same has high dielectric constant. Generally, since the chip varistor is made of materials having a high dielectric constant, if the area of both end portions contacting with an external electrode is larger, the capacitance is increased irrespective of the surface area of the internal electrode. Therefore, in order to decrease the capacitance, the varistor should be thinner for thereby decreasing the surface area of both end portions.
Generally, for allowing the capacitance of the varistor to be below 5 pF, the thickness of the varistor layer is formed to be below 1 mm. If the thickness of the varistor layer is below 1 mm, the varistor may be easily deformed or broken when sintering the same after stacking the varistors or when handling the same, so that it is impossible to fabricate a thinner varistor to meet a low capacitance requirement. Therefore, it is known that the stackable chip varistor can not have a capacitance below 1000 pF. Currently, the low capacitance chip varistor is not available in the industry. Therefore, a low capacitance chip varistor which has a low capacitance enough to be used for a high speed signal circuit and is not easily deformed and broken when fabricating and handling the same is desperately needed.